1. Field of the Invention
This invention relates to an indirect extrusion press, and more particularly, to an improved indirect extrusion press equipped with a hydraulic coupling device and capable of adding the container-shifting force to the extrusion force.
2. Description of the Prior Art
In a conventional indirect extrusion press illustrated in FIG. 1, a press platen 51 defining a through bore 51A and a main cylinder frame 52 are spacedly and oppositely disposed along the longitudinal center line of the press in the front and back positions respectively, and are rigidly connected together by means of tie rods 53 arranged in "X" patterns so as to form the press frame body into a Rahmen structure.
A main ram 55 is slidably received in a main cylinder 54 fixedly secured on the main cylinder frame 52. An extrusion force generating unit is constituted by the main ram 55, crosshead 56, pressing stem 71, etc. Crosshead 56 and main ram 55 are arranged in such a manner that they may be shifted forward namely, toward press platen 51) under no load by means of side cylinder devices, each of which devices includes a side cylinder 57 and piston 58. On the other hand, a die stem 74 of a cylindrical configuration is fixed on the press platen 51 along the longitudinal center line of the press, to which die stem 74 is mounted a die 73 via a die holder 72.
A container 70 can be freely shifted back and forth along the longitudinal center line of the press, namely, along the pressing direction by means of container-shifting cylinder devices, each of which is formed of a cylinder 61 and piston 62. The relative position of container 70 and pressing stem 71 can be fixed by means of hydraulic coupling devices, each of which is formed of a cylinder 59 and piston 60. Therefore, each of container-shifting cylinders 61 is attached to main cylinder frame 52 while each of hydraulic coupling cylinders 59 is secured to crosshead 56 and is slidably fitted through main cylinder frame 52. Furthermore, the pistons 60, 62, which are slidably received in their respective cylinders 59, 61, are coupled at their rearmost ends with a rear frame 76 provided integrally with the main cylinder 54 on the periphery of the latter. The rear frame 76 can axially be movable independently from main cylinder 54 insofar as a large ring-like bore is provided in the center of rear frame 76. Rear frame 76 and container holders 69 are mutually connected by means of tie rods 77.
In addition the above-described members or devices, numeral 63 indicates an intermediate frame which is freely shiftable by means of a hydraulic cylinder device including a cylinder 64 and piston 65. Intermediate frame 63 is fitted over die stem 74 through a guide block 75, etc. Intermediate frame 63 is equipped with a vertical shear device which includes a hydraulic cylinder 66 and piston 67. A shearing edge 68 is adapted to sever off a discard from an extruded article.
In the conventional indirect extrusion press shown in FIG. 1, a billet loaded in container 70 may be indirectly extruded through die 73 by shifting container 70 in such a manner that the container slides over die stem 74 while fixing the relative position of container 70 and pressing stem 71. Although the above-noted conventional press is constructed in such a manner that the container-shifting force may be added to the extrusion force of main cylinder 54 during each extrusion stroke, it is accompanied by following drawbacks.
Namely, the overall pressing force to be generated during an extrusion stroke is a combination of forces exerted on main cylinder 54 and side cylinders 57 as well as a force applied onto the container unit. In order to make the press capable of withstanding the overall pressing force, it is indispensable to make each constituent parts of the main structure, which is formed by pressing platen 51, main cylinder frame 52 and tie rods 53 connecting said platen 51 and frame 52 together into the Rahmen structure, more durable by a degree at least equivalent to the shifting force of the container unit. This certainly results in an increase in its number of constituent parts a complication of its structure and an increase in its weight.
The inventors of this invention have heretofore made a number of inventions, including, for example, copending U.S. patent application Ser. No. 199,626 filed Oct. 22, 1980, U.S. Pat. Nos. 4,251,202 and 4,230,661 and copending U.S. patent application Ser. No. 946,330 filed Sept. 27, 1978, all of which relate to an extrusion press or extrusion process.